This invention relates to optical communications systems and more particularly to systems based on the coherence properties of a continuous wave laser which simultaneously transmits a phase modulated and an unmodulated laser beam.
Heretofore optical communication systems have used light pipes as well as directional beams of light upon which information has been added for transmission. Systems using directional beams have employed very stable lasers for the carrier. These systems operate on the heterodyne principle and are subject to intercept by a system employing a local oscillator to mix with the direct or scattered beam.